Magnetron tube



Feb. 7, 1956 c. AZEMA 2,734,148

MAGNETRON TUBE Filed March 20, 1951 2 Sheets-Sheet 1 C. AZEMA MAGNETRON TUBE Feb. 7, 1956 2 Sheets-Sheet 2 Filed March 20, 1951 United States Patent MAGNETRON TUBE Charles Azema, Paris, France, assignor to Compagnie Generale de Telegraphe Sans Fil, a corporation of France Application March 20, 1951, Serial No. 216,540

Claims priority, application France April 3, 1950 4 Claims. (Cl. 315-39.61)

The present invention refers to magnetron tubes and more particularly to magnetron oscillators with cavity resonators whose oscillation frequency may be adjusted.

Tunable magnetrons of the prior art can be divided in two main classes. In the first one, the tuning of the whole anodic block is performed by alteration of one cavity resonator only; in the other class, the resonating frequency of all the cavity resonators is simultaneously adjusted by means of a device which is symmetrical with respect to the axis of the cathode.

Frequency adjustment performed by acting upon one cavity resonator only, presents certain disadvantages, namely that the effect on the whole of the anodic block is small and therefore a small range of frequencies is covered; further dissymmetry is introduced in the field with respect to the cathode axis, thus reducing the efficiency.

These disadvantages are avoided by a symmetrical adjustment. However, the latter calls for an accurate and complicated mechanical device which is expensive and fragile.

It is an object of the present invention to provide a new type of adjustable magnetron which does not present the above-mentioned disadvantages and which offers the advantages of a symmetrical adjustment and yet is of a simple structure. Another object of the invention is to provide an adjustable magnetron avoiding the use of straps for stabilizing its oscillation mode.

According to the invention, a magnetron having a cylindrical cathode and a concentric anodic block grooved with cavity resonators, hereinafter termed main cavity resonators, comprises an additional adjustable cavity resonator, hereinafter called auxiliary cavity resonator, which is simultaneously coupled to alternate main cavity resonators, the coupling means being symmetrical with respect to the cathode axis.

The invention will be better understood by reference to the following description and to the appended drawing showing non-limiting examples of embodiments of the magnetron according to the invention.

Fig. 1 shows a longitudinal section, by a plane passing through the axis of the cathode, of a magnetron according to the invention.

Fig. 2 is a section of the magnetron according to the invention by a plane perpendicular to the cathode axis and shows the distribution of the lines of force of the electric field.

Fig. 2a very diagrammatically shows a perspective view of the magnetron according to the invention with a portion cut away.

Fig. 3 is an equivalent diagram of the magnetron.

Fig. 4 shows a section of the magnetron according to the invention, by a plane comprising the axis of the magnetron, the latter being provided with a lateral auxiliary cavity resonator.

According to the embodiment shown in Figure 1, main cavity resonators provided in an anodic block 1 are coupled to a concentric auxiliary cavity resonator 5, by

2,734,148 Patented Feb. 7, 1956 means of elongated apertures 2 provided in the external wall of alternate main cavity resonators. concentrically with the anode, a cathode 3 is supported by rods 4 which also carry the heating current and the negative high voltage. The auxiliary cavity resonator 5 is provided with an aperture 6 for coupling to the load circuit, and its volume may be changed by means of a piston 7 fixed to a flexible membrane 8. Arrows 9 diagrammatically represent a mechanical device of any known type controlling the deformation of the membrane 8. The polar pieces of the magnet are shown in 10 and 11.

The external cavity resonator operates according to modes of H type which are symmetrical with respect to the magnetron axis, as shown in Figure 2. As the lines of force of the electric field have no transversal component, piston 7 may be mounted with some clearance with respect to the resonator walls.

Fig. 3 is the equivalent diagram of the anodic block. It comprises a network of 2 N poles, N being the number of main cavity resonators, each pair of poles being connected to an admittance Y1, and alternate admittances Y being respectively coupled through transformers T to variable impedances Z2, coupled to each other. Y1 represents a main cavity resonator, T the coupling apertures and the chain of impedances Z2 represents the auxiliary cavity resonator. The above system presents the following characteristics:

The variation of Z2 makes it possible to vary the resonance frequency of the network by adjustment of the values of Y1 and Z2;

The described system presents a rotational symmetry of the order N/2 around the axis. Therefore, the electromagnetic fields inside the magnetron will present the same symmetry;

It may be seen that by virtue of the coupling of alternate main cavity resonators to the auxiliary cavity resonator, the magnetron of the invention is made equivalent to a rising sun magnetron.

Accordingly, by a convenient choice of T and Z2, it is possible to avoid strapping.

Fig. 4 shows a section of another embodiment of the magnetron according to the invention by a plane comprising the magnetron axis. In this embodiment an auxiliary cavity resonator 5 still operating according to modes H, is coupled to alternate main cavity resonators by means of an apertured lateral wall 2. The volume of auxiliary cavity resonator 5 can be changed by means of a piston 7, fixed to a flexible membrane 8.

The operation of the embodiment of Figure 4 is exactly the same as in the case of Figure l, and the similar reference numbers represent therefore similar elements in both Figures 1 and 4.

What I claim is:

1. In a magnetron tube of the type comprising a cathode having an axis, an anode including a plurality of main cavity resonators, an auxiliary tunable cavity resonator, and means for coupling said auxiliary cavity resonator with said main cavity resonators: said coupling means being positioned in alternate main cavity resonators and symmetrically located with respect to the axis of said cathode.

2. In a magnetron tube of the type comprising a cathode having an axis, an anode including a plurality of main cavity resonators, an auxiliary tunable cavity resonator, and means for coupling said auxiliary resonator with said main resonators: said coupling means constituted by apertures respectively provided in alternate main cavities to connect said alternate main cavities with said auxiliary cavity, said apertures being symmetrical with respect to the axis of said cathode, the respective centers of said apertures being contained in the same plane.

3. A magnetron, tube comprising a cathode having. an axis, an anode including'a plurality of main cavity resonators, an auxiliary tunable cavity resonator, said tunable resonator being toroidal and coaxially surrounding said anode, a common Wall separating said auxiliary resonator and said main resonators, saicl common wall having apertures provided therein to connect alternate main cavity resonators with said auxiliary cavity resonator, said apertures being symmetrical with respect to the axis of said cathode, the respective centers of said apertures being contained in the same plane.

4. A magnetron tube comprising a cathode having an axis, an anode including a plurality of main cavity resonators, a lateral wall to close said" main resonators, an

auxiliary tunable cavity resonator, said auxiliary resonator being toroidal and adjacent to said wall, said wall being provided with apertures to connect alternate main cavity resonators With said auxiliary cavity resonator, said apertures being symmetrical with respect to the axis of the cathode.

References Cited in the file of this patent UNlTED STATES PATENTS 2,411,953 Brown Dec. 3, 1946 2,419,172 Smith Apr. 15, 1947 2,450,629 Bondley Oct. 5, 1948 2,466,060 Spencer Apr. 5, 1949 

